Raj,
The UML capabilities are available in or release 4.0 developmental milestone build which is in the Downloads section under ‘Development Releases’. To try it out, please use a fresh install of Eclipse 3.0.2, not one that is already associated with 3.8.4, to avoid any conflict or confustion. For production use, we still recommend 3.8.4, since 4.0 is still in development. However, we would encourage you to give it a try and provide feedback to us in the “All 4.0 Milestone Questions” forum.
Also, in the next day or two, we’ll have a new milestone available, 4.0M2, that will contain several bug fixes and many new features over the 4.0M1 release. If you don’t want to wait, you can give M1 a try now and then use the update site (once M2 is available) to update your installation.